Self cleaning centrifuge drum with stepwise variable closing pressure

ABSTRACT

A centrifugal separator constructed for performing full desludgings as well as partial desludgings during separation. One end member of the separating chamber is a piston valve movable axially to open and close sludge discharge openings disposed at the outer periphery of the drum. The axially outward disposed side of the piston valve is in sliding sealing engagemenet with confronting drum portion at radially spaced intervals so that a radial succession of divisions of the closing chamber is provided which can be filled up in a known manner with control fluid and selectively emptied for reducing the force acting on the piston valve and thereby performing a full desludging or a partial desludging.

United States Patent 1191 Hemfort 1 Oct. 16, 1973 [5 SELF CLEANINGCENTRIFUGE DRUM 3,189,267 6/1965 Thylefors 233/20 A WITH STEPWISEVARIABLE CLOSING 3,415,446 12/ 1968 Welland 233/20 R PRESSURE 2,840,3026/1958 Steinacker et aL... 233/20 A 3,550,843 12/1970 Hoffmann 233/20 Ainventor: Heinrich Hemfort, Oelde, Germany Assignee: Westfabia SeparatorAG,

Oelde/Westf., Germany Filed: Sept. 29, 1971 Appl. No.: 184,887

Foreign Application Priority Data 061. 2, 1 970 US. Cl 233/20 A Int. Cl.B04b 11/00 Field of Search 233/19 R, 19 A, 20 R,

References Cited UNITED STATES PATENTS l2/l958 12/1964 Stone Germany P20 48 429.1

Nyrop 233/20 A 7/1971 Steinacker 233/20 A Primary Examiner-George H.Krizmanich Attorney-Burgess, Dinklage & Sprung [5 7] ABSTRACT Acentrifugal separator constructed for performing full desludgings aswell as partial desludgings during separation. One end member of theseparating cham her is a piston valve movable axially to open and closesludge discharge openings disposed at the outer periphery of the drum.The axially outward disposed side of the piston valve is in slidingsealing engagemenet with confronting drum portion at radially spacedintervals so that a radial succession of divisions of the closingchamber is provided which can be filled up in a known manner withcontrol fluid and selectively emptied for reducing the force acting onthe piston valve and thereby performing a fun desludgin g or a partialdesludging.

3 Claims, 3 Drawing Figures PAIENIEDHBI 15 I915 4 FIG. I.

SHEET 10F 3 PATENTEnum 16 1975 3. 765.599

sum 2 or 3 PATENTEDum 16 I975 3. 765599 SHEET 30F 3 SELF CLEANINGCENTRIFUGE DRUM WITH STEPWISE VARIABLE CLOSING PRESSURE BACKGROUND Theinvention relates to self-cleaning centrifuge drums in which theseparating chamber and the sludge chamber are defined at one end by thepiston valve controlling the sludge discharge outlet apertures. Drums ofthis type of construction areprovided with a closing chamber locatedbetween the piston valve and the adjacent portion of the drum, which isfilled with a control fluid before the centrifuging to impose pressureon the piston valve to move the piston valve and thereby close thesludge discharge openings. The closing chamber has a greater radialexpanse than the sludge chamber, so that when the closing chamber iscompletely filled with fluid exerting closing pressure acting to closethe piston valve, the closing force on the piston valve is alwaysgreater than the force of the drum charge acting on the other sideurging the piston valve open. For the ejection of solids, control fluidis let out of the closing chamber with the drum running at fullspeed,'and thus the closing pressure is diminished. Under the pressureof the drum charge the piston valve then moves to the position in whichthe sludge discharge outlet apertures are uncovered.

Depending on the nature and consistency of the separated solids, it maybe advantageous to perform socalled partial desludgings at briefintervals of time, with occasional full desludging operations at longertime intervals.

When partial desludging is performed, the sludge discharge outletapertures are opened only slightly and/or for a brief period, so thatonly a portion of the accumulated solids in the sludge chamber isejected, while the rest remains as a safety ring within the drum. Thisprevents any great amount of product fluid from being ejected with thesolids and going to waste.

When full desludging is performed, the drum is opened wide and theentire contents of the drum is ejected. To achieve a thorough cleaning,full desludging is often followed by a rinsing operation in which thedrum is filled with fresh water and spun to empty it again.

To limit the length of time and the degree to which a self-cleaning drumis opened for partial discharge purposes, the drum can be so constructedthat a portion of the closing fluid (the fluid in the closing chamberurging the piston valve toward the closed position) remains in theclosing chamber. After the ejection of solids commences, as soon as thefluid level in the separating chamber has receded to such an extent thatthe opening pressure is lower than the closing pressure of the closingfluid remaining in the closing chamber, the piston valve immediatelymoves back to the closed position. The greater the closing pressure ofthe control fluid retained in the closing chamber is, the more rapidlythe drum recloses and the less solid matter is ejected in each openingoperation.

A drum of different construction, having a closing chamber that does nothave to be emptied, is shown for example in German Pat. No. 1, 055,451.With this prior-art drum both partial and full desludging can beperformed, depending on how long an opening chamber is kept filled withcontrol fluid. This time-dependent control, however, is quite criticalin the performance of partial desludging, because the time it takes tofill the opening chamber of that device is dependent upon the waterpressure, and is a portion of the time that has to be preset in acontrol apparatus.

But even in the case of a drum having a piston valve which defines oneside or end of the separating chamber, it is a known porcedure to retaina portion of the closing fluid in the closing chamber. GermanAuslegeschrift Pat. No. 1,432,760 discloses a plurality of designpossibilities for achieving this.

According to one of these proposals, a conical plate is inserted intothe closing chamber to divide the outer portion of the chamber into twoaxially opposite chambers. The outlet passage, which is controlled by avalve, extends from the periphery of the lower chamber. When this valveis opened for the ejection of solid matter, the closing fluid in theupper chamber of the outer portion of the closing chamber alwaysremains, and causes the piston valve to move to its closed positionwhenever the fluid level in the separating chamber recedes and thepressure on the top side of the piston valve has become lower than thepressure of the retained closing fluid acting on its bottom side. Withthis drum, however, only partial desludging can be performed.

According to another proposal set forth in German Auslegeschrift Pat.No. 1,432,760, the lower portion of the drum is provided at variousdistances from the axis of rotation with outlet bores for closing fluid,which extend from the closing chamber. The closing chamber extends overthe entire radial expanse of the piston valve. These bores can beselectively stopped with plugs, so that the level of the retainedclosing fluid can be adjusted to different distances from the axis ofrotation. The orifice of these bores on the outside of the drum areuncovered by an axially movable valve at predetermined intervals of timefor the purpose of the ejection of solid matter. With this drum it ispossible to adjust the draining of the closing fluid such that eitherfull desludging can be performed, or partial desludging operationsadapted to the specific weight of the mixture being centrifuged.

If the outlet bores on the periphery of the closing chamber areuncovered, the chamber is completely emptied upon the opening of thevalve and thus a full desludging is performed. The closer the openoutlet bores are to the axis of rotation, the more closing fluid is leftin the closing chamber, and only partial desludging can be performed.

In order to change over from full desludging to partial desludging, andto adapt the level of the retained closing fluid to the specific weightof a different mixture, the drum has to be stopped and at least partial]disassembled.

THE INVENTION The invention is first addressed to the problem ,ofcreating a centrifuge drum which selectively permits the performance ofpartial and full desludging operations without shutting down theseparator.

In further development of this main idea, it will be possible in astep-wise manner to vary the closing pressure of the retained closingfluid during operation.

The invention is characterized by the fact that the piston valve, inaddition to its customary guidance, is additionally guided sealingly onthe adjacent drum portion at different distances from the axis ofrotation and thereby divides the closing chamber into a plurality ofradially successive divisions which can be fed with control fluid in aknown manner and can be selectively emptied through passages which leadoutwardly from the peripheral portions of the individual divisions. Inthe case of simultaneous emptying of all divisions, the closing pressureis completely eliminated, so that full desludging operations can beperformed.

When only one or several of the divisions are emptied, a portion of theclosing fluid is retained, so that partial desludging can be performed.

The radial dimensions of the individual divisions can be such thatdifferent partial pressures result, which individually or in combinationpermit extensive adaptation of the residual closing pressure to thespecific weight of the mixture being centrifuged and of the solids beingseparated.

Thus, in summary, the invention is concerned with a centrifugalseparator constructed for intermittent discharge of sludge, comprising arotatably mounted separator drum having a separating chamber defined byan upper end member and a lower end member, and at least one sludgedischarge passageway disposed at the radially outward periphery of thedrum. One of said end members of the separating chamber is a pistonvalve movable axially to open and close the sludge discharge passagewayfor desludging Fluid operated piston valve control means are providedfor alternately forcing the piston valve to the closed position by afluid pressure created in a closing chamber by feeding a control fluidthereto and permitting the piston valve to move to an opened position bydraining off the control fluid therefrom. Further included are controlfluid routing means for controlling the position of the valve. Theinvention provides the improvement which comprises the piston valvecontrol means including a plurality of divisions of the closing chamberdisposed in radial succession from the axis, provided by concentricslide seals between the axially outwardly disposed surface of the pistonvalve and the confrontlng drum portion. The control fluid routing meansincludes means for connecting the different divisions of the closingchamber with the infeed of the control fluid and means for selectivelydepressurizing of the different divisions of the closing chamberpermitting selection of the force imposed on the piston valve.

A number of embodiments of the invention are represented in the drawing.

FIG. 1 shows a centrifuge drum in which the closing chamber is dividedinto two divisions which can be emptied selectively through valves whichare held in closing position by feeding a liquid thereto and brought tothe open position by shutting off the infeed. (In each of the figures,the piston valve is shown in the closed position (sludge dischargepassageways closed) on the left of the figure, and in the open positionon the right side. Also, like reference characters refer tocorresponding parts.)

FIG. 2 shows the same drum, in which the valves are normally in closedposition and brought to the open position by the infeed of fluid, and

FIG. 3 shows a centrifuge drum in which the closing chamber is dividedinto three divisions from whose peripheral portions calibrated boreslead outward.

With reference to FIG. 1, a separating and sludge chamber is provided byseparating section 1 and sludge section 2. The chamber is defined byupper end member 3a and lower end member 3, which is a piston valvewhich is axially movable. Axial movement of piston valve 3 opens andcloses the sludge discharge apertures 4 for the ejection of solids.Between the piston valve 3 and the lower drum wall 5 is located theclosing chamber which in the present embodiment is divided so as toprovide two chambers or two divisions 6 and 7, which are sealed from oneanother and are at different radial distances from the axis so that theyare disposed in radial succession from the axis, the piston or slidevalve 3 being not only sealingly guided in the conventional manner at 8and 8a, but being also sealingly guided at 9 on the adjacent drum part5.

The separator includes control fluid routing means for pressurizing anddepressurizing of control fluid for controlling the position of thepiston valve. Outlet passages 10 and 11 run from the radially externalend of divisions 7 and 6, respectively, and are controlled, respectivelyby fluid controlled valves 12 and 13. These valves are held in theclosed position by the constant infeed of fluid and are brought into theopen position by shutting off the feed of fluid. Their manner ofoperation is described in detail in the copending German Pat.application P 20 22 197.0 of the assignee hereof; U.S. Ser. No. 139,078filed Apr. 30, 1971, also of the assignee hereof.

Prior to the opening of the inlet (not shown) for the liquid that is tobe separated, control valves 14 and 15 in control fluid infeed conduitsor lines 16 and 17 are opened, this being brought about in the presentembodiment by the control apparatus 18. The control fluid passes fromfeed line 16 through bore 19 into the receiving groove 20 and from feedline 17 through bore 21 into the receiving groove 22. From the receivinggroove 20 the control fluid flows first through the passage 23 whichruns out radially and brings the valve 12 into the closed position. Thereceiving groove 22 communicates with valve 13 through a passage 24, sothat this valve, too, shifts to the closed position.

The controller 18 can actuate the various valves such as 14 and 15 tocontrol desludging in dependence on operation of the separator, e.g.,based on a time interval or operation, e.g., properties of product.

After passage 23 is filled up, the control fluid passes in known mannerfrom the receiving groove 20 to the closing chamber, passing in thepresent embodiment through one or more passages 25 into the outerdivision 7 of the closing chamber, and through one or more passages 26into the inner division 6 of the closing chamber. In both instances,control fluid overflows from groove 20 in the respective bores leadingto the respective chamber divisions. The sum of the closing forcesproduced in divisions 6 and 7 is equal to the closing force which thecontrol fluid would produce in an undivided closing chamber. The fillingup of divisions 6 and 7 brings the piston valve 3 into the closedposition (left side of FIG. 1).

After a certain quantity of solid matter has collected in the sludgechamber 2, the outlet valve 12 is opened by the closing of valve 14 inthe control fluid infeed line 16 and the outer division 7 is therebyemptied, while the closing fluid is retained in the inner division 6.

Starting with both valves 14 and 15 open, by the closing of valve 15 inthe control fluid infeed line 17, the outlet valve 13 is opened and thepressure in the inner division is thereby relieved since the fluid canthen run freely through the inner division, while the closing fluid isretained in the outer division 7. In both cases partial desludging isperformed. The individual closing pressures in divisions 6 and 7 can bedifferent. The piston valve 3 moves to the open position (right side ofFIG. 1) and immediately moves back to the closed position whenever theopening pressure has become lower than the closing pressure of theretained closing fluid as a result of the receding liquid level inseparating chamber 1.

The closing of both valves 14 and 15 brings both outlet valves 12 and 13into the open position and both divisions 6 and 7 are emptied so thatthe drum is completely emptied.

To avoid the trouble that would develop if excess control fluid were topass over from receiving groove into receiving groove 22, receivinggroove 20 is provided with an overflow pipe 27 to limit the fluid levelto prevent overflow from groove 22 into groove 20, the diameter of theoverflow lip 28 is made larger than that of of the annular flange 29which separates grooves 20 and 22.

In the embodment in FIG. 2, the outlet valves 12 and 13 are closed inthe fluid-free state and are brought into the open position by theinfeed of control fluid. The manner of operation of such valves is alsodescribed in detail in copending German Pat. application P 20 22 197.0,U.S. application Ser. No. 139,078 filed Apr. 30, 1971, both assigned tothe assignee hereof. This embodiment is advantageous wherever there is ashortage of fresh water and its consumption must be kept down. The drumshown in FIG. 2 requires three infeed lines 30, 31 and 32 for controlfluid with valves 33, 34 and 35, respectively, and three separatereceiving grooves 36, 37 and 38. When valves 33 and 35 are closed, theoutlet valves 12 and 13 are also closed. when valve 34 opens, controlfluid flows in a known manner through the aperture 39 into the receivinggroove 36 and thence through passages and 26 to the inner and outerdivisions 6 and 7 of the closing chamber. After both divisions have beenfilled up, the piston valve 3 is in the closed position and the fluidinfeed can be shut off.

After a certain amount of solid matter has built up in the sludgechamber 2, the outlet valve 12 or 13 can be put into the open positionby a selective, momentary opening of valve 33 or 35, these outlet valvesbeing fed with control fluid from bores 67 and 68 through receivinggrooves 38 and 37, respectively, and passage 69 and 70, respectively. Inthis manner the inner division 6 or the outer division 7 of the closingchamber is emptied and a partial desludging is performed. By thesimultaneous opening of both valves 33 and both divisions 6 and 7 areemptied and full desludging is performed. To prevent the overflow ofcontrol fluid from one receiving groove into another, overflow bores 40and 41 are provided for the two upper grooves 36 and 37, respectively,while overflow lip 42 of the bottom groove 38 has a larger diameter thanthe annular flange 43.

In the embodiment represented in FIG. 3 the closing chamber is dividedinto three divisions 44, 45 and 46 of successively greater radius by thefact that the piston valve 3 is sealingly guided at 47 and 48 inaddition to the conventional guidance it has at 8 and 8a. Instead ofoutlet valves such as 12 and 13 in FIG. 1 for controlling flow from thechamber divisions calibrated bores are used, the bores permitting asmall bleed stream to be discharged continously from the chamberdivisions when the divisions hold fluid under pressure. If infeed to adivision is shut off, the division empties as calibrated bores 49,50 and51 lead outward from the peripheral portion of divisions 44,45 and 46.

The control fluid is fed in through separate lines 52. 53 and 54, intowhich valves 55, 56 and 57, respectively, are installed. It passes inknown manner through bores 58, 59 and 60 into receiving grooves 61, 62and 63, and thence through passages 64, 65 and 66 to divisions 46,45 and44, respectively of the closing chamber. This drum, like the one in FIG.1, requires a constant infeed of control fluid.

If all three valves 55, 56 and 57 are simultaneously closed the controlfluid is dumped by centrifugal force from the three divisions 44,45 and46 through the calibrated bores 49, 50 and 51.

Upon the selective closing of the individual valves or of two valves incombination, partial desludging takes place. The closing force of theretained fluid can be varied step-wise over a wide range.

EXAMPLE Let us say that the radial dimensions of the individualdivisions 44, 45 and 46 are such that the fluid in the inner divisionproduces three twelfths, the fluid in the middle division produces fourtwelfths and the fluid in the outer division produces five twelfths ofthe total closing pressure. The following closing pressure settings arethen possible.

I Inner chamber only 3/12 of the total closing pressure II Middlechamber only 4/12 of the total closing pressure III Outer chamber only5/12 of the total closing pressure IV Inner middle chamber 7/12 of thetotal closing pressure V nner outer chamber pressure 7 VI Middle outerchamber 9/12 of the total closing pressure VII Inner middle outerchamber total closing pressure Any other desired division can, ofcourse, be chosen.

The closing chamber may also be divided into four or more divisions,thereby appreciably increasing the number of possible combinations.

Also, it is possible to provide the drum in FIG. 1 withcalibrated'outlet bores instead of outlet valves, or the drum in FIG. 3can be equipped with valves as'in FIGS. 1 or 2 instead of calibratedbores as in FIG. 3. The control fluid infeed passages must then bearranged in accordance with the construction of the drum. With the drumsof the invention it is possible selectively to perform full or partialdesludging without any conversion, and, in the performance of partialdesludging, to adapt the closing pressure of the retained fluid to thespecific weight of the liquid being centrifuged and to the solid matterbeing separated.

What is claimed is:

1. In a centrifugal separator constructed for intermittent discharge ofsludge, comprising:

a. a rotatably mounted separator drum having an upper end member and alower end member defining a separating and sludge chamber, at least onesludge discharge passageway disposed at the radially outward peripheryof the drum,

b. one of said end members including a piston valve movable axiallywithin said chamber to open and 8/12 of the total closing 12/12 of theclose the sludge discharge passageway for desludging,

d. a fluid operated piston valve control means for alternatively forcingthe piston valve to the closed position by the pressure of a controlfluid and permitting the piston valve to move to an open position byrelieving the pressure of the control fluid,

d. control fluid routing means for pressurizing and depressurizing ofcontrol fluid for controlling the position of the piston valve,

the improvement which comprises:

e. said piston valve having an axially outwardly disposed surface, andsaid drum having a surface confronting said surface of the piston valve,said piston valve control means comprising a plurality of closingchambers disposed in radial succession from the axis, concentric slideseals between the axially outwardly disposed surface of the piston valveand said confronting drum surface, providing said plurality of closingchambers,

f. said control fluid routing means comprising means for selectivelypressuring and depressurizing of the closing chambers permittingselection of the force imposed on the piston valve.

2. Separator according to claim 1, said control routing means comprisingfluid controlled valves for closing and opening of the control chambersfor, respectively, pressurization and depressurization of control fluidtherein.

3. Separator according to claim 1, said control fluid routing meanscomprising conduits outfitted with control valves for controlled routingof the control fluid and a controller for controlling operation of thecontrol valves in dependence on operation of the separator.

1. In a centrifugal separator constructed for intermittent discharge ofsludge, comprising: a. a rotatably mounted separator drum having anupper end member and a lower end member defining a separating and sludgechamber, at least one sludge discharge passageway disposed at theradially outward periphery of the drum, b. one of said end membersincluding a piston valve movable axially within said chamber to open andclose the sludge discharge passageway for desludging, d. a fluidoperated piston valve control means for alternatively forcing the pistonvalve to the closed position by the pressure of a control fluid andpermitting the piston valve to move to an open position by relieving thepressure of the control fluid, d. control fluid routing means forpressurizing and depressurizing of control fluid for controlling theposition of the piston valve, the improvement which comprises: e. saidpiston valve having an axially outwardly disposed surface, and said drumhaving a surface confronting said surface of the piston valve, saidpiston valve control means comprising a plurality of closing chambersdisposed in radial succession from the axis, concentric slide sealsbetween the axially outwardly disposed surface of the piston valve andsaid confronting drum surface, providing said plurality of closingchambers, f. said control fluid routing means comprising means forselectively pressuring and depressurizing of the closing chamberspermitting selection of the force imposed on the piston valve. 2.Separator according to claim 1, said control routing means comprisingfluid controlled valves for closing and opening of the control chambersfor, respectively, pressurization and depressurization of control fluidtherein.
 3. Separator according to claim 1, said control fluid routingmeans comprising conduits outfitted with control valves for controlledrouting of the control fluid and a controller for controlling operationof the control valves in dependence on operation of the separator.